[Spike]

C4 will renew it, no CBB ruined the start of the year for them and the share for January was the worst for C4 in some years. So it would be even worse if there was no mains series.
A digital channel wouldn't pick it up because as Matt said Hijack showed Big Brother isn't popular for a digital channel.
ITV would probably bid because it does better than most of the stuff thats it shows in the 9pm/10pm slots now and their Friday ratings could do with a boost. It would probably do well on ITV1 and the weekend ratings would increase because of its strong line-up but as soon as there was a poor series of a week of bad ratings ITV would move it around the schedules and even axe it
BBC would never go for it, its not their type of show and they couldn't justify spending the licence fee on Big Brother
Five would bid for it and might even be successful. They are starting to bid for a few shows which will cost them lots like Premiership highlights, Uefa Cup, soaps and a few US shows, so I could really see them bidding for it as it would boost the rest of their schedule.

When the rights are for sale it will be a 3 way battle between ITV1, C4 and Five. With C4 or Five probably winning